The Rural Voice, 1989-06, Page 32PASTURE MANAGEMENT
AND LIVESTOCK HEALTH
1,17
r les
by Suzanne Lovegrove
It has often been claimed that the
improvement of pasture establishment
and management methods has been
accompanied by an increase in
problems affecting grazing animals.
Some of these problems are prob-
ably exaggerated, but it is important to
understand the causes of nutritional
disorders related to grazing, how they
relate to forage -management practices,
and how they can be controlled, treat-
ed, and, more importantly, prevented.
Following is a survey of some of
the more common stresses caused by
grazing and brief descriptions of
methods of control or prevention.
Bloat
This is probably the most common
of diet -related health problems in ru-
minants. It is more common in dairy
animals (cow or goat) than in sheep or
beef cattle because the dairy animal is
likely to be fed larger amounts of
legumes such as clover or alfalfa.
In addition to the increased use of
legumes in high-quality pastures, other
factors contributing to bloat are more
intensive management systems and,
possibly, the increased use of fertil-
izers in pasture production.
Bloat is usually caused by animals
overeating in succulent green pastures.
Frosted, wet, or rapidly growing
legumes are most dangerous, but
wheat, oats, rye, and lush grasses may
also cause trouble. Hay will not
normally cause severe bloat, although
overfeeding green, high-quality alfalfa
hay, particularly if it has been har-
vested from fields heavily fertilized
with nitrate, can cause problems.
The obvious answer is to control
feeding. It is wise to feed a meal of
hay before allowing access to spring
pastures and to let any dew on
legumes dry before turn -out in the
morning. Ideally, a good -quality grass
hay should be available overnight.
Pasture -management measures
include seeding grass -legume mixtures
rather than legumes alone, using
bird's -foot trefoil (a legume known for
its no -bloat characteristics), intensive
strip grazing, or cutting and feeding
legumes as green feed in a dry lot.
A seemingly logical approach to
controlling bloat would be the routine
addition of foam -breaking (and
therefore bloat -preventing) agents to
feed. Some of the compounds that
have been tested include vegetable
oils, animal fats, paraffin, turpentine,
and silicones. Vegetable oils and
animal fats are quite effective, but
their effect is generally only short-
lived (two or three hours).
To be safe and effective, one dose
of anti -foaming agent should work
against bloat for at least 12 hours, act
within 10 minutes, not be eliminated
in milk or cause ill effects on repro-
duction, feed intake, milk quality, or
general health, and not be present in
body tissues after five days. It must
30 THE RURAL VOICE
1